1. Field of the Invention
The present invention relates to a fixed pattern noise correction circuit that removes noise included in an image signal output from an image sensor, to an imaging apparatus including such fixed pattern noise correction circuit, and to a fixed pattern noise correction method applied to an imaging apparatus.
2. Description of the Related Art
In the past, a variety of solid-state imaging apparatuses that use a sensor such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor have been developed and commercialized. Such solid-state imaging apparatuses may have fixed pattern noise that is present at the same pixel positions irrespective of time. One example of a known type of fixed pattern noise is in the form of vertical lines (i.e., perpendicular lines). That is, when a CMOS image sensor is constructed such that one circuit is used for each column of pixels in the vertical direction, noise in the form of vertical lines is produced due to nonuniformity in the characteristics of the circuits used for the respective columns of pixels.
A number of methods for correcting noise in the form of vertical lines have been proposed. However, when such vertical lines are corrected during digital signal processing, the detected vertical line components are subtracted from the original image signal, and therefore it is difficult to correct noise in the form of vertical lines at a level not determined by quantization of the image signal.
Also, when an image of a high-luminance subject is captured using a solid-state imaging apparatus, there are cases where noise referred to as “streaking” is produced in the horizontal direction in the captured image. As one example, it is possible to correct streaking by correcting differences in DC level compared to when image is captured with pixel portions shielded from light. Japanese Unexamined Patent Application Publication No. 2005-130331 discloses one example of such a method for correcting streaking.